Central nervous system (CNS) responds to traumatic injury to spinal cord in a complex way that includes secondary injury, endogenous repair, and cortical reorganization. The ultimate neurological status of spinal cord injured subjects is determined both by the state of the injured cord tissue and cortical plasticity. However, relatively little is known about the role of cortical organization on the neurological status in spinal cord injured victims. Such knowledge is crucial for instituting and objectively evaluating appropriate interventional strategies in spinal cord injury (SCI). We propose to perform in vivo magnetic resonance imaging (MRI), including functional MRI (fMRI), to follow ongoing pathologic changes in the cord tissue and plastic changes in the brain in experimental SCI. These in vivo studies will be combined with cellular and morphological techniques to assess the synoptic and dendritic densities brain tissue. In addition, we will examine the effect of treatment with neurotrophic factor NT3 that is shown to elicit axonal growth in the spinal cord, on the cortical reorganization. The data gained from these experiments should prove to be crucial for understanding the mechanisms used by CNS to adapt to the injured state. In addition, these studies will also represent the first attempt to use these combined approaches to study how a potential therapeutic intervention in the spinal cord might modify the brains potential to respond to injury. This information may lead to the development of novel strategies to combine brain plasticity with spinal cord repair, to enhance recovery. With recent advances in the treatment of SCI, there is a critical need to noninvasively monitor the efficacy of a given treatment. The proposed MRI and fMRI studies greatly aid realize this goal.